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[aprssig] APRS resolution and symbols

Keith VE7GDH ve7gdh at rac.ca
Thu Oct 4 11:46:48 UTC 2007


Bob WB4APR wrote...

> Things move pretty slowly. WIDEn-N came out in 1998, 10 years
> ago, and look at how long it is taking to get HAMS to change
> from RELAY and WIDE..

I think it really comes down to the fact that a lot of the problems (e.g.
RELAY, WIDE) were originally written into the APRS spec, and that APRS
keeps getting tweaked and changed with "shoot from the hip" improvements.
I'm not saying that change is bad... just that the APRS spec is a moving
target rather than something that was robust right from the time it was
released. It doesn't help that there are (at least after the "recent" path
changes in North America) probably thousands of web sites that still suggest
obsolete settings. Those needed improvements have also fragmented the
APRS community with some areas still using RELAY and WIDE (obsolete
in North America) because some digi operators are either slow or reluctant
to update their settings, and with other areas (notably in Europe) left with
just as much of a problem with cross-border interoperability unless the
users have the ability to change their path on the fly.

> Throwing out all backwards compatibility to 30,000 users so that a few
> people who can have GPS resolution to 2 centimeters but who then
> cannot be seen by any one else, just undermines APRS communications
> integrity.

I think that talking about resolution in APRS vs OpenTRAC is a red herring.
If there was ever a move to OpenTRAC (or any other protocol) it would most
definitely NOT be because of "near survey grade" GPS resolution. It would be
for other reasons.

> When the whole point of APRS is to promote consistent
> information communications between users. The APRS spec does contain
> resolution to 1 foot that IS backwards compatible to ALL 30,000
> users.  No need to re-invent the wheel...

I agree completely that it would not be a good thing to obsolete everything
that everyone is now using. That just wouldn't be acceptable. If there was
ever a popular move towards OpenTRAC on 144.390, it would have to be because
of compelling reasons, and done in such a way that the infrastructure
maintained backwards compatibility for existing APRS users at least between
themselves, the digis (which wouldn't have any trouble supporting both) and
the IGates & the APRS-IS.  It may not ever happen, but I think we should
keep an open mind to change.

> Not true. Adding the symbol-a-week guarantees a loss in
> communications integrity when not everyone has the new symbol
> sets every-week. As a case in point, it seems to take YEARS for
> most clients to implement a changed SYMBOL set even when we only
> add a few per year!  Imagine how impossible it would be to
> communicate if all clients had to keep up with the new symbol
> table of the week...

Just what were the "symbol-a-week" changes over the last two or three years?
I do recall the addition of a TRACTOR a year or so back. Someone asked and
almost instantly, they got it. If "you" keep adding a few new symbols per
year, the symbol set will be changing almost constantly at a trickle rate
for years and years to come. If there is "now" room to add many more
symbols, they should be hammered out in a timely manner and written into the
spec and not added piecemeal a few at a time.

> Back in 1996 we increased APRS from one symbol byte (91 symbols)
> to two bytes yielding over 3200 potential symbols.  At that time
> there were 700 defined, but WinAPRS wanted no more because each
> additional one required special coding. This summer, APRS1.2
> (which the new Kenwoods have already adopted) is expanding the
> use of that symbol set. Just a month ago, we defined a new
> symbol "O-" for OPERATOR PRESENT.

If that argument was maintained, it would mean never changing (improving)
APRS just to satisfy WinAPRS users. While there are many thousands of
UI-View users, the APRS spec also isn't going to remain static just to
satisfy the UI-View users, just like the spec isn't going to be changed to
intentionally obsolete a particular APRS client. Changes if any should be
done because they are needed. However, if the APRS spec ever changes
so much that it obsoletes existing software, that is a bridge that will have
to be crossed then.

> And every time you bring this up, I tell you that the only
> reason that HUMAN symbol was initially called a JOGGER was
> because in APRSdos, the only menu key I had at the time (1997)
> was "J".  And back then I was trying to keep an association
> between each letter of the alphabet and each symbol for easy
> entry.  But that was 10 years ago.  Now selections are not made
> by name any more!  So it is not a jogger, it is a human figure.

There are many places where the HUMAN symbol is referred to as the JOGGER
symbol. I can understand the logic of J for JOGGER if the "J" key was the
only one available at the time for APRSdos. I'll do my best to refer to it
as a HUMAN symbol in future.

> If you look at the SYMBOL definitions, you will see that the
> symbol is named HUMAN. And I still hold back on wasting symbol
> sets for trying to define such meaningless differentiations
> between  Standing, Walking or Hiking HUMANS!

Yet there are differentiations between BOY SCOUT and GIRL SCOUT and so on.
They could have just (at least now) been different underlays for the HUMAN
symbol.

 > How is the SKIER with a tracker and an HT going to change his
> symbol from a SKIER to a HIKER or to a WALKER each time he
> takes his skis off, or changes from boots to shoes?

That to me is absurd. The SKIER symbol would be used for the entire duration
of the trip. The use of the SKIER symbol would be to indicate that skis were
the primary means of transport on a particular trip. However, with the
ability to "switch profiles" in devices like the TT3 or OT, it would be
trivial (the addition of a SPST switch) to change to the CAMPGROUND symbol
while they were camped instead of actually moving.

> To satisfy your complaints about the skier symbol, I have now
> added the symbol "S[" as a skier, so that we don't have to
> re-hear this complaint every winter...  How many years will it
> be now until ALL software authors implement it? And not until
> all of them do, will you have any assurance that what you send
> will be displayed as intended.

I thank you for that! I've asked about a skier symbol perhaps 2-3 times a
year for the last three years. The first few times, you made arguments for
there not being any characters available to use for a new symbol. The last
few times, I was ignored... or at least I don't recall seeing any comments
from you the last few times I dropped the hint. How many years will it take
for all software authors to implement it? I don't know, but it sure didn't
take very long for the UI-View symbol set too be updated to add the TRACTOR
symbol... which to me was really a waste of a symbol when your argument was
that there were no characters available and whatever other changes were done
at the time. If there are 3200 characters available now, I would have no
argument against the TRACTOR symbol. Back when there were only half a dozen
or so available, I would have thought that a tractor would have been just
fine using a TRUCK symbol, and the handful of tractor operators could have
just added "tractor" or "farm tractor" to their beacon comment. If the
floodgates are now open and if there is a demand for new symbols, now would
be the time to open the discussion on the subject. If the symbol sets used
by the various APRS clients will need to be updated, it will be less work
for the various authors and others that contribute to the updates to do them
all in one go instead of updating it now to add the skier symbol, next year
for a couple more and the following year for a handful more.

A final question... just who is it that decides if new symbol(s) will be
added when requested, or if any other suggests are adopted into the APRS
spec? The APRS spec refers to an "APRS Working Group" and mentions several
well known names. Does that group or a modified list still exist? I know you
are passionate about APRS and this isn't meant to denigrate the hard work
you and others have done over the years. I'm just trying to clarify if the
working group still exists or if decisions are solely yours. I know I asked
this a few years ago, but I don't recall a clear answer.

73 es cul - Keith VE7GDH
--
"I may be lost, but I know exactly where I am!"





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